Ubuntu lucid, dell xps 13 (geforce 9500m).
When I turn the laptop on, I always get an error in kern.log and fail to load X with nvidia. If I reboot several minutes later, it is sometimes fixed - and sometimes it is not.
I attach the bug report, but here are the immediately relevant lines from kern.log:

Sorry for not answering - I had to make sure my solution works, and so far it does.

Thank you very much for your help. It seems that the problem is not with nouveau, as it was not solved by blacklisting it. The problem is that ubuntu pre-loads the driver vga16fb in order to enable plymouth graphical boot.